Smartgauge w/ 3 batterys

[lateral]

Originally Posted by ramblinrod

A Smart Gauge only measures voltage and time. You can do the same thing with a $10 DVM and the ships clock or your phone clock. You can assure your 50% reading is accurate by assuring there is no significant load nor charge. Guess what, when you wake up in the morning and nothing is on, and the sun is very low angle, there is no load and no charge. 12.2 Vdc = 50%. If it reads higher you are golden.

Similarly, at sunset, you have had diminishing charge from solar for some time. At sunset, with normal load (fridge running) if you read 12.75 Vdc, you are 100%.

With these end points, about as accurate as one can get with any tool, one has all they really need.

At any time during the day, one can estimate SOC based on voltage, current, and sun intensity. This is even better than what a Smart Gauge can do. It has no idea what the current is, and why a Smart Gauge is not accurate while charging, which can all waking hours with solar or 24/7 with wind.

Do not be fooled. A Smart Gauge measures voltage and time. That is all. Based on those readings and past trends it guesses at what is going on. A man with a DVM and a clock can do exactly the same thing, only better, he can also see the sun shining, see the wind generator turning, know what loads are on, and shut them off, to take measurements.

Do you think you can easily transfer this "ability" to your crew/person using your boat?

[john61ct]

Originally Posted by ramblinrod

A Smart Gauge only measures voltage and time. You can do the same thing with a $10 DVM and the ships clock or your phone clock.
...
With these end points, about as accurate as one can get with any tool, one has all they really need.
...
A Smart Gauge measures voltage and time. That is all. Based on those readings and past trends it guesses at what is going on. A man with a DVM and a clock can do exactly the same thing

Sorry, again just wrong.

That "man with a DVM" may **think** he's getting good accuracy, but most of the time only in the sense that a stopped clock is right twice a day.

Just repeating it over and over doesn't make it true.

At least use an accurate ammeter at the top end.

I think the fundamental issue here is that you just don't think it's an important issue.

[ramblinrod]

Originally Posted by lateral

Do you think you can easily transfer this "ability" to your crew/person using your boat?

Yes, anyone who has some cognitive ability can learn that 12.2 or more in the morning is good and less than 12.7 at sunset is bad.

Its about as easy as more than 50 in the morning is good and less than 95 at sunset is bad.

My wife, bank manager by career, wakes in the morning before me and says, "12.4 and the forecast is full sun; yippee we won't have to start the engine today."

Else, "12.2 and overcast, I'll start the engine. Warm water this morning; yippee!

What's hard about that?

[Bleemus]

At this point just agree to disagree. I will take Johns approach. No offense to Rod but I prefer a more scientific approach. I am a geek so I have no defense. A fan of the SG for me and my guests. Bleemus out.

[lateral]

I just like the cross reference concept, even if the crew are no slugs at DC theory.
I am a closet geek and budget gear hunter as well. SG cost me $150.

[john61ct]

For those who do want to buy one, I highly recommend supporting Maine Sail for his priceless work advising the community over the years.

http://www.pbase.com/mainecruising/smart_gauge

Extra cost is less than you'd spend stopping for a fast food meal with the family.

If anyone finds it wanting put up on eBay I'll probably buy it 8-)

And yes I also have a Victron 702-BMV

[Zil]

I have six 6 volt GC batteries in a 12 volt bank. I have a switch to disconnect the entire bank in emergency or for maintenance. If one battery has problem, it will take a second to disconnect the bank. A minute to find the troubled battery with a meter. Another minute to pull the terminal fuse to isolate that battery. A second to switch on for a reduced bank.
There is a limit to what i could bring along, so the complicated equipment needed for a 20 hour test was left behind.
I trust my Victron counter, but I also monitor charging amps against charging volts.
If I could buy a Smart Gauge at half price as u-all do, I would have one.
This thread deteriorated rapidly. A shame.

[sailcrazy]

Zil-We have almost an identical batt system installed, except I put a On/Off sw on each pair of batts before the power gets to the busbar that combines all 3, and then an On/Off sw on the busbar output to the house fuse and Dist Pnl. And you're right-the scheme has worked very well. But which Victron counter do you use, and is it on just the combined 6-batt output? Our Link 20 system is on its last legs and needs to be replaced. And, based on comments made on this thread I'm leaning away from using a Smart Gauge as we have solar and wind installed(continuous charging).

[john61ct]

The Victron 700 series is current, but 600 is fine.

702-BMV has an extra muli-function sensor port, can be used with an even-number-batt bank to sense and alarm (or trigger the relay to isolate) based on a voltage differential between the two halves.

This should help identify an internal problem with one batt, before it causes catastrophe.

Also can be a temp sensor or 2nd-bank voltmeter.

Would be silly IMO to buy a BM for each block in a paralleled bank.

Every switch and device in there adds resistance and risk of failure.

KISS a very important principle on a boat, always a balancing act

[john61ct]

Originally Posted by Zil

This thread deteriorated rapidly.

Diversity of opinion is a good thing, disagreement can help everyone learn, and off the wall ideas can advance best practices eventually.

Just takes some long familiarity with the various posters to figure out whose opinions to pay more or less attention to.

[Zil]

I have the Victron BMV 700. It monitors my house bank. Three neg cables from the 3 sets of GC2 batteries to one side of the 500 amp shunt. The other side of shunt goes through disconnect switch to the negative buss bar. I use the built in relay to turn on my battery box ventilation fan. It serves me well. It was purchased from Compass Marine based Rod's recommendation and lower cost. I see Rod now has the Blue Sea monitor as well. https://shop.marinehowto.com/t/batte...oring-products

[sailinglegend]

Originally Posted by ramblinrod

Do not be fooled. A Smart Gauge measures voltage and time. That is all.....

Now you really are showing your ignorance. You should read a bit more about Smartgauge before becoming so opinionated.

Here is what the designer Chris Gibson has said:

Full post is at,

Smartbank battery management - Page 2
post number #42

Obviously I am not prepared to disclose how SmartGauge works. Anyone who asks me to do so is simply being totally unreasonable.
But to say that only voltage can be measured via 2 wires is *completely* incorrect.....
Pull a brief current pulse from the battery and measure the voltage drop, this will give an indication of internal resistance.
Present an AC voltage across the battery and measure the phase angle and amplitude of the resultant current. This will show the AC impedance of the battery.
Do the same thing with a wide variety of frequencies and analyse the results. This is know as AC impedance spectrography.

I have a signature that I very occasionally use - in this case it is relevant.

Ignorance isn't what you don't know but what you think you know that is incorrect!

[Stu Jackson]

Originally Posted by sailcrazy

Zil-We have almost an identical batt system installed, except I put a On/Off sw on each pair of batts before the power gets to the busbar that combines all 3, and then an On/Off sw on the busbar output to the house fuse and Dist Pnl. And you're right-the scheme has worked very well. >>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>

Hi, for you and zll, have either of you had the need to actually USE this?

[sailcrazy]

Stu Jackson.....no, thankfully, not since I installed our current scheme. But previously, my boat had 2 D-8's for batteries. Just the night before we were to leave for an 8-week sail around the Philippines, we were onboard completing some last minute issues and I just happened to put my hand on the settee cushion that was over our battery compartment-and it was HOT!!! No other warnings! That battery was so hot I could have fried an egg on it. The next day (obviously we did not leave that next morning) we had tied a cats cradle around the battery (thats about 175lbs of battery and sulfuric acid as I recall) and were pulling it up the companionway via a fiddle block secured to the boom, and the line broke just as we got it up to the companionway entrance. It fell down, spilling acid and breaking the foot of the person below(I was on top, pulling it up). After we got back from the hospital, I promised myself that was the last big battery I would ever have below. I redesigned the entire DC system, including using 6-6v batteries, with an ON/Off sw on each 12v cell so it can be easily and quickly isolated from the system. And so far-we've never had to use it.......yet!

[Stu Jackson]

sc, thanks for the feedback. I agree that monster batteries are killers, literally and figuratively. Thanks again.